A LIST OF THE ROTATORIA OF WASHINGTON AND 

 VICINITY, WITH DESCRIPTIONS OF A NEW GENUS 

 AND TEN NEW SPECIES. 



By Harry K. Harking, 



Of the United States Bureau of Standards, Washington, D. C. 



INTRODUCTION. 



The investigation of the Rotatorian fauna of this region was begun 

 about five years ago, and has revealed an entirely unsuspected wealth 

 of rare and undescribed species. In the appended list are recorded 

 236 previously described species. As far as practicable preserved 

 material of these has been deposited in the National Museum, so that 

 their identity may be verified. A large number of new species have 

 been found; of these 10 are here described and figured. 



It should not be inferred that Wasliington affords unusual oppor- 

 tunities for collecting Rotatoria, or that any vast territory has been 

 overrun; nearly the entire list is based on collections made in the 

 old Fish Ponds, now filled in, the ponds at Kenilworth, District of 

 Columbia, and Lakeland, Maryland, swamps and ponds at Four-Mde 

 Run, Vii'ginia, and occasional trips to Black Pond, Virginia, and 

 Glenburnie, Maryland. But little work has so far been done on the 

 Potomac River. 



For the determination of most of the BdeUoids I am indebted to 

 Mr. David Bryce, of London, England, who has at all times placed 

 his unsurpassed knowledge of this group at my disposal. 



For the illustrations an arbitrary sliding scale has been used; for 

 an animal measuruig 100 pt a size of 50 mm. was selected and for 

 each succeeding 100 fj. 10 mm. added, so that the size of the illus- 

 tration is 40 mm. + 10 mm. for each 100 fx of the total length. 

 While no doubt objections may be urged against this arrangement, 

 it has the advantage of keeping figures of the largest Rotatoria 

 within the limits of an octavo page, while the smallest are 

 sufficiently large to show the necessary detail. For the trophi a 

 base size of 25 mm. for an actual 10 fx has been used, adding 2.5 mm. 

 for each succeeding 10 fi; the size of the illustration thus becomes 

 22.5 mm. + 2.5 mm. for each 10 /( of the length. 



Proceedings U.S. National Museum, Vol. 46— No. 2032. 



387 



